Please review my fix for 8165372 : "StackWalker performance regression
8147039 reimplemented stack walking using javaVFrames in place of
vframeStream, in order to give correct results for the experimental
LiveStackFrame feature. However, this also resulted in a significant
StackWalker performance regression (25-60%, depending on specific
operation and stack depth).
This fix includes stack walking implemented both ways, encapsulated
within C++ classes. JavaFrameStream provides the speed we had before
for most use cases, while LiveFrameStream provides correct results when
Performance is much improved, back within 5% or so of pre-8147039
levels, based on my measurements.